1. Field of the Invention
This invention relates to a gas insulated switch which opens and closes within a vessel filled with arc-extinguishing gas (e.g. SF.sub.6), for switching an electric current below a rated load of a system.
2. Description of the Prior Art
In recent years the need for the simplification and economic utilization of switchgear in electric power systems has led to a requirement that isolators also have a load current switching capability.
In the conventional switching circuit illustrated in FIG. 1, the power-source side P and load-side L of two sets of bus-bar lines A and B are connected in common, and one system can be cut off by forming a loop through the switches C.sub.a and C.sub.b.
In this case, parallel-break contacts are used for the switches C.sub.a and C.sub.b ; but in some cases, when these switches do not provide sufficient circuit-breaking capability, the latter is increased by the adoption of gas-puffer type contacts.
However, the gas-puffer type of switch itself requires considerable power to operate it, and its construction is complicated, so that it is uneconomic when only a small breaking capacity is required.